When Colombia's new president, Andrs Pastrana, goes to Washington this week, he'll put on display his high hopes of ending Latin America's last cold-war-era civil conflict.

But his quickly arranged visit to Capitol Hill Thursday also reveals growing concerns that peace possibilities could be jettisoned by a continuing US insistence on putting Colombia's drug fight ahead of efforts to negotiate with the country's rebels.

"Anywhere democracy is threatened in the hemisphere, we have to consider that is against our interests," says one US official. He adds that, if the guerrillas are able to intimidate their way to greater political authority, "that concerns us for Colombia and the region."

But last week the US House of Representatives voted to hold back antidrug aid if Colombia goes ahead with government troop pullout plans. President Pastrana has committed to an initial demilitarization of 4 percent of territory in the country's southern war zone - a heavy coca-growing region - as part of an initial negotiation process.

As the war goes on, Colombia's neighbors, including Venezuela, Panama, Ecuador, and Brazil, have expressed growing concerns over its possibly destabilizing "spillover effect." Colombia's displaced people have crossed borders, while the Army has entered neighboring countries in pursuit of rebels. The guerrillas are believed to be holding some of their prisoners in Ecuador.

The US-Colombia dustup comes just as more Colombians than ever sense an opportunity to bring their ravaged country peace.

For 13 years Colombia's Palace of Justice has sat bombed out and closed in the heart of Bogot, an unhealed reminder of the war with leftist guerrilla groups that has left the country one of the world's most violence-torn: more than 200,000 Colombians dead, with hundreds of thousands more displaced, disappeared, and abducted.

But today, after a repair project that has seemed as interminable as the civil war, the Palace of Justice renovation is nearing completion - converting the building into a new symbol of hope that perhaps Colombia, too, is nearing peace.

That new hope is based on the inauguration in August of Mr. Pastrana, who has made arriving at a lasting peace his first priority. Pastrana has vowed to lead peace negotiations himself beginning as early as November.

But ironically the new hope also derives from the evolution of a civil war that has intensified and extended its impact over the past two years as a result of a strengthened insurgency. The guerrillas are estimated by some observers to hold effective control over as much as half of Colombian territory. Much of it is unpopulated jungle, but the psychological effect is still strong.

The government is proceeding with plans for a despeje, or clearing out of all armed forces (though a maintaining of state authority) in five municipalities of southern Colombia. That area could then be the site of negotiations - and an example of how a broader drawing back of belligerent forces might work.

Just arriving at an agenda for negotiations will be complex enough. The guerrillas have long demanded land reform and other elements of "social justice," but just where their political ideology stands after the international tarnishing of their Marxist principles is unclear. "[The guerrillas'] marriage with the narco-traffickers has eroded their ideological base," says Sergio Uribe, a Colombian political analyst. "With their huge income they've become a bunch of capitalists."

But even US sources say the guerrillas have a "social agenda" that will have to be addressed.

"I don't buy the idea some put forth of 'narco-guerrillas,' " says the US official mentioned above, referring to the thesis of some observers that Colombia's guerrillas have degenerated into common drug traffickers devoid of any other cause. The guerrillas have said they are ready to give up their drug-related earnings in exchange for programs offering poor rural farmers viable agricultural alternatives.

A war that for years was considered by many urban Colombians to concern only the military and the guerrillas is now having a broad impact on all Colombian society.

In the post-cold-war era, Latin America's leftist revolutionaries are supposed to be either converts to democracy or simply irrelevant - even Fidel Castro now speaks of armed insurgency as a method of the past. Now some foreign analysts including US officials consider Colombia's fortified guerrillas - and the threat they pose to an intact Colombia - as worrisome destabilizing factors for Latin America.

The war's impact throughout the country and the region is causing a traditional Colombian indifference to be replaced by a palpable desire for peace. Last October Colombians surprised everyone when 10 million voted in a grass-roots peace referendum. Then, in this year's presidential elections, absenteeism dropped from a traditional 60 percent to about 40 percent - a turnout interpreted by many observers as both a political defeat for the guerrillas and a strong sign of support for Pastrana's focus on peace negotiations.

"You used to hear people all the time say, 'This conflict doesn't matter to me, it doesn't affect me,' but that's changed," says Gabriel Murillo, a political scientist at the University of the Andes in Bogot. The war is now having a growing impact on a national economy long thought immune. Colombian cities are bulging with the war's displaced - numbering more than 1 million - and the long-held assumption that the Army would some day defeat the guerrillas is no longer valid.

Perhaps the thorniest initial issue to settle for negotiations is simply who participates. Leaders of the country's 4,000 paramilitary soldiers say they must be at the table, but the guerrillas want nothing of that. "We've seen a proliferation of actors in this conflict that can only make its resolution more problematic," says Mr. Murillo. "In Central America's conflicts you basically had the state and anti-state," he adds, "but in Colombia there is a complex multipolarity."

And that's not even taking into consideration what some analysts consider the essential participation of parties from outside Colombia. They say no resolution is possible without the participation of the US. Tacitly recognizing this, guerrillas are calling on Europe to become involved as a counterbalance. With Colombia seen as the hemisphere's worst human rights offender, organizations like Amnesty International should also take part, others say.

Finally, but perhaps most important, there will have to be a deep sense of national pardon for such a long conflict to really end in peace. Pastrana recognizes this, having recently called for a full pardon of the guerrillas.

The rebels have good historical reason to be wary of such offers. The M-19 group that stormed the Supreme Court building in 1985 was practically wiped out by political violence after it converted to a legitimate political party. Still, Colombia's conflict and the threat it poses to a stable hemisphere will end only when Colombians are able to look beyond their past. "For there to be peace in Colombia," says Mr. Uribe, "we'll have to be able to forgive and forget."